The methyl green-pyronin procedure uses the high net
negative charge of nucleic acids. Methyl green is a cation
which binds rather specifically to DNA and thus serves as a
convenient means of staining nuclei in both f ixed material
and living cells. Pyronin, a red dye, is fairly specific for
RNA with some binding to protein.

Control slides are important in interpreting the
results of methyl green-pyronin staining, since the
procedure is readily susceptible to artifact. One or both of
the nucleic acids should be removed either enzymatically or
by acid extraction.